Carburetor provided with auxiliary fuel feed means

ABSTRACT

A carburetor for internal combustion engines having a passage controlled by a throttle valve, in which an auxiliary fuel injection nozzle is provided which is open in said passage at a location which will be upstream of the throttle valve when said throttle valve is in a closed position and downstream of the throttle valve when said throttle valve is in a slightly opened position, and from which auxiliary fuel is injected into said passage during light-load (i.e. throttle valve slighty open), high speed operation of the engine.

United States Patent [191 [111 3,761,063

Shibanaka et al. Sept. 25, 1973 CARBURETOR PROVIDED WITH 3,333,833 8/1967 Bimberg 261/41 D AUXILIARY FUEL FEED MEANS 3,554,173 1/1971 Masaki et al.

. 3,588,058 6/1971 Lucas 261/69 A [75] Inventors: Akita Shibanaka, Hiroshima-shi;

Harumi Takayama, Chiba-ken, both of J p Primary ExaminerTim R. Miles [731 Assignees; Toyo Kogyo Ltd Attorney-Stevens, Davis, Miller & Mosher Hiroshima-ken; Nippon Carburetor Co., Ltd., Shinagawa-ku, both of Japan 57 ABSTRACT [22] Filed: Apr. 5, 1971 A carburetor for internal combustion engines having a 21 A 1. N 131,165 1 pp 0 passage controlled by a throttle valve, in which an auxiliary fuel injection nozzle is provided which is open in [30] Foreign Application Priori y Data said passage at a location which will be upstream of the Apr. 16, 1970 Japan 45/36944 throttle valve when said throttle valve is in a closed position and downstream of the throttle valve when said [52] U.S. Cl. 261/41 D, 261/69 A throttle valve is in a slightly opened position, and from [5-1] Int. Cl. F02m 7/04 which auxiliary fuel is injected into said passage during [58] Field of Search 261/69 R, 69 A, 41 D light-l ad (L rottle alv slighty p g sp d operation of the engine. [56] References Cited UNITED STATES PATENTS 4 Claims, 2 Drawing Figures 3,167,599 1/1965 Brown et al. 261/41 D 7 I2 I?) 5 4 2| 5 w CARBURETOR PROVIDED WITII AUXILIARY FUEL FEED MEANS This invention relates to a carburetor for automobile internal combustion engines which contributes to the prevention of misfire or irregular combustion in the engine and to the prevention of the car knocking phenomonon, and more specifically to a carburetor provided with auxiliary fuel feed means by which the intake mixture is maintained at an adequate mixing ratio during the high speed operation of the automobile with a throttle valve being slightly opened.

A carburetor for automobile internal combustion engines is generally set such that an intake mixture of an adequate mixing ratio will be obtained in the low speed or low r.p.m. region of the engine in which the engine is mostly operated. Therefore, there is the tendency that the fuel-air mixing ratio becomes somewhat lower than actually required, in the high r.p.m. region of the engine. Particularly in the light load, (i.e., throttle valve slightly open) high speed operation or the high r.p.m. region of the engine the mixture becomes excessively thinner than required because the quantity of the intake air is relatively small and the quantity of fuel injected from the main fuel injection nozzle of the Venturi is relatively small though the manifold vacuum pressure is high, and thus car knocking has resulted due to misfire or irregular combustion.

The object of the present invention is to provide a carburetor in which is provided means for correcting the mixing ratio of the mixture so as to meet the demand of the engine during the high r.p.m. region of said engine with the throttle valve being slightly open (light load), by feeding auxiliary fuel to the engine, and thereby to eliminate the disadvantage set forth above.

According to the present invention, an auxiliary fuel injection nozzle of an auxiliary fuel feed means is provided adjacent the throttle valve at a location which will be upstream of the throttle valve when said throttle valve is in a fully closed position and downstream of the throttle valve when said throttle valve is in a slightly opened position. Valve means is also provided to permit a fuel supply to said nozzle when the manifold vacuum pressure downstream of said thorttle valve reaches a value greater than a set value. Fuel is injected'from said auxiliary fuel injection nozzle when the throttle valve is oened to a certain degree and the manifold vacuum pressure is higher than the set value, whereby the intake mixture of a mixing ratio suitable for such operating condition of the engine can be obtained.

The above and other objects and advantages of the invention will become apparent from the following description and the accompanying drawings:

FIG. 1 is a cross-sectional view of an embodiment of the carburetor according to the present invention which is provided with auxiliary fuel feed means; and

FIG. 2 is graph showing the relationship between the engine r.p.m. and the fuel flow, using the manifold vacuum pressure as a parameter.

Referring to the drawings, a two stage dual barrel type carburetor has an auxiliary fuel feed device on a primary barrel 1. Although the drawings show a two stage dual barrel type carburetor, since the barrel of an ordinary one stage carburetor corresponds to the primary barrel of such a two stage dual barrel type carburetor, the present invention can be practiced by providing the auxiliary fuel feed device on the barrel of the ordinary one stage carburetor.

The primary barrel 1 comprises a choke valve 2, a Venturi 3, a main fuel nozzle 4, a butterfly throttle valve 5, and an idling fuel port 6a and a slow port 6b. A secondary barrel 7 is provided with a Venturi 8, a main fuel nozzle 9, a throttle valve 10 and a slow 11 located slightly upstream of a fully closed position of said throttle valve 10. The slow port Ill is connected with a low speed fuel passage 12 formed in the side wall of the barrel 7. The above-described construction is the same as that of conventional carburetors.

In the primary barrel 1 is formed an auxiliary fuel injection nozzle 13 adjacent the throttle valve 5 at a location which will upstream of the throttle valve 5 when said throttle valve is in a fully closed position and downstream of the throttle valve 5 when said throttle valve is in a slightly opened position. The auxiliary fuel injection nozzle 13 communicates through a jet l4 and an on-off valve 15 with fuel chamber 17 the wall of which is partially constituted by a diaphragm l6. Auxiliary fuel is supplied from the air bled, low speed fuel passage 12 in the secondary barrel through a branched passage 18 into the fuel chamber 17. On the other side of the diaphragm 16 is formed a vacuum chamber 19 which communicates through a vacuum passage 20 with an inlet passage downstream of the throttle valve 5 and including the inlet manifold of the engine, to take the manifold vacuum pressure therefrom. The on-off valve 15 has a valve body 22 connected to the diaphragm 16. The valve body 22 is urged by a spring 21 into mating engagement with avalve seat 23 to shut down the auxiliary fuel supply to the injection nozzle 13. The arrangement is such that the on-off valve 15 will be opened when the vacuum pressure introduced into the vacuum chamber 19 through the vacuum passage 20 reaches a value greater than a set value.

The manifold vacuum pressure is extremely high when the engine is in the idling operation or the engine brake is in effect, with the throttle valve 5 being fully closed. In this case, therefore, the valve body 22 is disengaged from the valve seat 23 under the effect of the vacuum pressure acting in the vacuum chamber 19 through the vacuum passage 20. However, since the auxiliary fuel injection nozzle 13 is located upstream of the throttle valve 5, the manifold vacuum pressure does not act at the injection nozzle 13 and hence auxiliary fuel is not injected from said injection nozzle.

In the operation of the engine with the throttle valve 5 being slightly opened, the auxiliary fuel injection nozzle l3is located downstream of the throttle valve 5. In this case when the engine r.p.m. is low although somewhat higher than idling speed (for example 1,000 to 2,000 r.p.m.) in the manifold vacuum pressure is lower than the set value, so that the on-off valve 15 is held in the closed position and auxiliary fuel is not fed in spite of the fact that the injection nozzle 13 is located downstream of the throttle valve 5. On the other hand, in this case when the engine r.p.m. is high enough to be greater than the set value, the injection nozzle 13 is opened by way of the diaphragm l6 and thus auxiliary fuel is sucked into the intake mixture to be mixed therewith. Namely, a mixture of a mixing ratio suitable for the high speed operation of the engine with the throttle valve being slightly open can be obtained with high combustion efficiency.

As the throttle valve 5 is further opened, the manifold vacuum pressure becomes lower than the set value, so that the on-off valve 15 is closed under the biasing force of the spring 21 and the feeding of auxiliary fuel is interrupted.

Namely, in the present invention auxiliary fuel is fed only when the engine is in the so-called light-load, high speed operation wherein the throttle valve 5 is in the slightly opened position and the manifold vacuum pressure is higher than the set value, as in the case when the automobile is driven on a slow descending slope with a slight pressure being applied to the accelerator pedal.

FIG. 2 shows the relationship between the engine rpm. and the adequate fuel flow when the manifold vacuum pressure is -500, -400 and -300 mmI-Ig which pressures are adjusted by controlling the opening degree of the throttle valve. In the graph of FIG. 2, the solid curves represent the characteristic of the subject carburetor provided with the auxiliary fuel feed device and the dotted curves represent the characteristic of buretor and the conventional carburetor (the curves of both carburetors are exactly overlapped in the chart). In the so-called light-load operation wherein the degree of opening of the throttle valve is small (e.g., in the case of the manifold vacuum pressure being -400 or -500 mmHg in FIG. 2) and when the engine speed is high, the fuel flow does not increase to the required quantity in case of the conventional carburetor as indicated by the dotted curves, so that the mixture becomes excessively thin causing various objectionable phenomena as set forth previously. However, in the case of the subject carburetor auxiliary fuel is added under such operational condition of the engine and the fuel increases substantially in proportion to the engine speed as indicated by the solid curves. Therefore, a mixture to meet the demand of the engine can be obtained and the conventional disadvantages can be eliminated.

Although in the embodiment described herein the fuel is supplied to the auxiliary fuel injection nozzle through the low speed fuel passage 12 formed in the wall of the secondary barrel, it should be understood that the fuel may be supplied to said injection nozzle directly from the float chamber or the main fuel passage. The fuel passage conncting the auxiliary fuel injection nozzle with the fuel source is preferably provided independently from a passage which supplies fuel to the idling fuel port or the slow port, so that the idling operation of the engine is not disturbed by the auxiliary fuel supplied to the auxiliary fuel injection nozzle.

Further, although the present invention has been described and illustrated herein with reference to a specific embodimnt thereof, it should be understood that the invention is not restricted to the details of the embodiment but many modifications and changes are possible within the scope of appended claims. For instance, the on-off valve 15 in the embodiment described may be replaced by a diaphragm switch which operates upon sensing the manifold vacuum pressure and a solenoid valve which opens and closes a passage leading to the auxiliary fuel injection nozzle.

We claim:

1. A carburetor including at least one barrel having a first passage therethrough, a main fuel nozzle, a Venturi, an idling fuel port and a throttle valve for controlling a supply of intake mixture to an engine wherein the improvement comprises:

a. an auxiliary fuel injection nozzle open to said first passage, said injection nozzle being located at a position which is upstream of said throttle valve when said throttle valve is in a closed position and which is downstream of said throttle valve when said throttle valve is in a slightly open position;

. a second fuel passage connecting said auxiliary fuel injection nozzle with a fuel source; and

c. valve means connected to said second fuel passage for opening and closing said second fuel passage, said valve means including means responsive to the manifold vacuum pressure downstream of said throttle valve for opening said second fuel passage when the manifold vacuum pressure exceeds a predetermined value, said second fuel passage being open to allow auxiliary fuel to be added to the intake mixture when the engine is in a relatively high speed operation with the throttle valve slightly open.

2. A carburetor according to claim 1 wherein said barrel has a slow port open to said first passage, said slow port being adjacent said throttle valve, said auxiliary fuel injection nozzle being located adjacent said slow port.

3. A carburetor according to claim 1 wherein said valve means comprises a vacuum chamber having a diaphragm as one wall, a third vacuum passage connected to said vacuum chamber for introducing the manifold vacuum pressure into said vacuum chamber, a valve body secured to said diaphragm and adapted to open and close said second fuel passage incident to movement of said diaphragm, and a spring urging said valve body into a closed position.

4. A carburetor according to claim 1 wherein said second fuel passage connecting said auxiliary fuel inpendently from a fuel passage leading to said idling fuel port.

t w a: 

1. A carburetor including at least one barrel having a first passage therethrough, a main fuel nozzle, a Venturi, an idling fuel port and a throttle valve for controlling a supply of intake mixtuRe to an engine wherein the improvement comprises: a. an auxiliary fuel injection nozzle open to said first passage, said injection nozzle being located at a position which is upstream of said throttle valve when said throttle valve is in a closed position and which is downstream of said throttle valve when said throttle valve is in a slightly open position; b. a second fuel passage connecting said auxiliary fuel injection nozzle with a fuel source; and c. valve means connected to said second fuel passage for opening and closing said second fuel passage, said valve means including means responsive to the manifold vacuum pressure downstream of said throttle valve for opening said second fuel passage when the manifold vacuum pressure exceeds a predetermined value, said second fuel passage being open to allow auxiliary fuel to be added to the intake mixture when the engine is in a relatively high speed operation with the throttle valve slightly open.
 2. A carburetor according to claim 1 wherein said barrel has a slow port open to said first passage, said slow port being adjacent said throttle valve, said auxiliary fuel injection nozzle being located adjacent said slow port.
 3. A carburetor according to claim 1 wherein said valve means comprises a vacuum chamber having a diaphragm as one wall, a third vacuum passage connected to said vacuum chamber for introducing the manifold vacuum pressure into said vacuum chamber, a valve body secured to said diaphragm and adapted to open and close said second fuel passage incident to movement of said diaphragm, and a spring urging said valve body into a closed position.
 4. A carburetor according to claim 1 wherein said second fuel passage connecting said auxiliary fuel injection nozzle with said fuel source is provided independently from a fuel passage leading to said idling fuel port. 